An image sensor is a semiconductor device which is configured for capturing radiation and converting the sensed radiation into electric signals. Generally, an image sensor includes a Photo Diode (PD) which is photosensitive and a logic circuit adapted to convert light sensed by the PD into electric signals. The logic circuit generally includes a transfer transistor, and the PD is connected with a Floating Diffusion (FD) region through the transfer transistor. When the image sensor operates, a transfer transistor is opened, and thus, photo-induced carriers in the PD can be transmitted into the FD region through a channel in the transfer transistor.
In an existing image sensor, transmission efficiency of photo-induced carriers being transmitted from a PD into a FD region is relatively low. More information about transmission efficiency of photo-induced carriers in an image sensor can be found in a Chinese patent application publication No. CN101752395A, published on Jun. 23, 2014.
Therefore, an image sensor and a manufacturing method thereof are required, to improve transmission efficiency of photo-induced carriers.